An internal combustion engine of the above-stated type is used as a drive for motor vehicles. Within the context of the present disclosure, the expression “internal combustion engine” encompasses diesel engines and spark-ignition engines and also hybrid internal combustion engines, that is to say internal combustion engines which are operated using a hybrid combustion process.
Internal combustion engines have at least one cylinder head and one cylinder block which are connected to one another at their assembly end sides so as to form the individual cylinders, that is to say combustion chambers. The cylinder head often serves to hold the valve drive. It is the task of the valve drive to open and close the inlet and outlet openings of the combustion chambers at the correct times.
To hold the pistons or the cylinder liners, the cylinder block has a corresponding number of cylinder bores. The piston of each cylinder of an internal combustion engine is guided in an axially movable manner in a cylinder liner and, together with the cylinder liner and the cylinder head, delimits the combustion chamber of a cylinder. Here, the piston crown forms a part of the combustion chamber inner wall, and together with the piston rings, seals off the combustion chamber with respect to the cylinder block or the crankcase, such that no combustion gases or no combustion air pass into the crankcase, and no oil passes into the combustion chamber.
The piston serves to transmit the gas forces generated by the combustion to the crankshaft. For this purpose, the piston is articulatedly connected by means of a piston pin to a connecting rod, which in turn is movably mounted on the crankshaft.
The crankshaft which is mounted in the crankcase absorbs the connecting rod forces, which are composed of the gas forces as a result of the fuel combustion in the combustion chamber and the mass forces as a result of the non-uniform movement of the engine parts. Here, the oscillating stroke movement of the pistons is transformed into a rotating rotational movement of the crankshaft. Here, the crankshaft transmits the torque to the drivetrain. A part of the energy transmitted to the crankshaft is used for driving auxiliary units such as the oil pump and the alternator, or serves for driving the camshaft and therefore for actuating the valve drive.
Generally, and within the context of the present disclosure, the upper crankcase half is formed by the cylinder block. The crankcase is complemented by the lower crankcase half which can be mounted on the upper crankcase half and which serves as an oil pan. Here, to hold the oil pan, that is to say the lower crankcase half, the upper crankcase half has a flange surface. In general, to seal off the oil pan or the crankcase with respect to the environment, a seal is provided in or on the flange surface. The connection is often provided by means of screws.
To hold and mount the crankshaft, at least two bearings are provided in the crankcase, which bearings are generally of two-part design and comprise in each case one bearing saddle and one bearing cover which can be connected to the bearing saddle. The crankshaft is mounted in the region of the crankshaft journals which are arranged spaced apart from one another along the crankshaft axis and are generally formed as thickened shaft extensions. Here, bearing covers and bearing saddles may be formed as separate components or in one piece with the crankcase, that is to say with the crankcase halves. Bearing shells may be arranged as intermediate elements between the crankshaft and the bearings.
In the assembled state, each bearing saddle is connected to the corresponding bearing cover. In each case one bearing saddle and one bearing cover—if appropriate in interaction with bearing shells as intermediate elements—form a bore for holding a crankshaft journal. The bores are conventionally supplied with engine oil, that is to say lubricating oil, such that a load-bearing lubricating film is ideally formed between the inner surface of each bore and the associated crankshaft journal as the crankshaft rotates—as is the case in a plain bearing. Alternatively, a bearing may also be formed in one piece, for example in the case of a composite crankshaft.
To supply the bearings with oil, a pump for feeding engine oil to the at least two bearings is provided, with the pump supplying engine oil via an oil circuit to a main oil gallery, from which ducts lead to the at least two bearings. To form the main oil gallery, a main supply duct is often provided in the cylinder block, which main supply duct is aligned along the longitudinal axis of the crankshaft.
A pump may be provided with engine oil originating from an oil pan via a suction line which leads from an oil pan to the pump, and said pump may ensure an adequately high feed flow, that is to say an adequately high feed volume, and an adequately high oil pressure in the supply system, that is to say in the oil circuit, in particular in the main oil gallery.
It is also normally necessary for the camshaft receptacle of a valve drive to be supplied with lubricating oil, for which purpose a supply duct is provided. The statements already made above with regard to the crankshaft bearing arrangement apply analogously. Further consumers to be supplied with lubricating oil may for example be the bearings of a connecting rod or the bearings of a balancing shaft which may be provided if appropriate. Likewise a consumer in the above sense is a spray oil cooling arrangement which, for the purpose of cooling, wets the piston crown with engine oil by means of nozzles from below, that is to say at the crankcase side, and therefore uses oil, that is to say is supplied with oil. A hydraulically actuable camshaft adjuster or other valve drive components, for example for hydraulic valve play compensation, likewise have a demand for engine oil and require an oil supply.
The friction in the consumers to be supplied with oil, for example the bearings of the crankshaft or between the pistons and cylinder liners, is dependent significantly on the viscosity and therefore the temperature of the oil which is provided, and said friction contributes to the fuel consumption of the internal combustion engine.
It is fundamentally sought to minimize fuel consumption. In addition to improved, that is to say more effective, combustion, the reduction of friction losses is in the foreground of the efforts being made. Reduced fuel consumption also contributes to a reduction in pollutant emissions.
With regard to reducing friction losses, rapid heating of the engine oil and fast heating-up of the internal combustion engine, in particular after a cold start, is expedient. Fast heating of the engine oil during the warm-up phase of the internal combustion engine ensures a correspondingly fast decrease in viscosity, and therefore a reduction in friction and friction losses.
Previous systems may actively heat the oil by means of an external heating device. The heating device is however an additional consumer with regard to fuel usage, which contradicts the aim of reducing fuel consumption.
In other concepts, the engine oil which is heated during operation is stored in an insulated container and utilized on demand, for example in the event of a re-start of the internal combustion engine. A disadvantage of this approach is that the oil which is heated during operation cannot be kept at a high temperature indefinitely, for which reason re-heating of the oil is generally necessary during the operation of the internal combustion engine.
Both an external heating device and also an insulated container result in an additional installation space requirement in the engine bay, and are detrimental to the attainment of the densest possible packaging of the drive unit.
The reduction of friction losses by means of rapid heating of the engine oil is also hindered in that the cylinder block and the cylinder head are thermally highly loaded components which require effective cooling and which are thus often equipped with cooling jackets for forming a liquid-type cooling arrangement. The thermal management of a liquid-cooled internal combustion engine is then influenced primarily by said cooling arrangement. Here, the cooling arrangement is designed with regard to protecting against overheating and not with regard to the fastest possible heating of the engine oil or of the internal combustion engine after a cold start.
Equipping the internal combustion engine with a liquid-type cooling arrangement requires the provision of coolant ducts which conduct the coolant through the cylinder block, that is to say at least one coolant jacket. Here, the coolant, generally a water-glycol mixture containing additives, is delivered by means of a pump arranged in the cooling circuit, such that said coolant circulates in the coolant jacket. The heat dissipated to the coolant is discharged from the interior of the cylinder block in this way, and is generally extracted from the coolant again in a heat exchanger.
In relation to other coolants, water has the advantage that it is non-toxic, readily available, and cheap, and furthermore has a very high heat capacity, for which reason water is suitable for the extraction and dissipation of very large amounts of heat, which is generally considered to be advantageous. By contrast, disadvantages include the corrosion, associated with water, of the components charged with coolant, and the relatively low maximum admissible coolant temperature, which significantly co-determines the temperature difference between the coolant and the components to be cooled and thus the heat transfer.
If it is sought to extract less heat from the internal combustion engine, in particular from the cylinder block, the use of other cooling liquids, for example of oil, may be expedient. Oil has a lower heat capacity than water and can be heated more intensely, that is to say to higher temperatures, whereby the cooling power can be reduced. The corrosion problem is eliminated. Oil can thus come into direct contact with—in particular moving—components without posing a risk to the functionality of the internal combustion engine.
Furthermore, the use of oil as coolant has further advantages, in particular the advantage that oil-type cooling and the associated coolant jackets may be formed coherently with the oil supply of the internal combustion engine, that is to say a common coherent oil circuit can be formed.
According to the previous systems, for fast heating of the internal combustion engine after a cold start, it is often the case that at least one valve is provided in the coolant circuit which valve prevents the circulation of the coolant in the coolant circuit during the warm-up phase.
Control of the liquid-type cooling arrangement is basically sought with which not only the circulating coolant quantity or the coolant throughput can be reduced after a cold start, but rather also the thermal management of the internal combustion engine heated up to operating temperature can be influenced.
Accordingly, a liquid-cooled internal combustion engine comprises a cylinder block which serves as an upper crankcase half and equipped with at least one integrated coolant jacket; an oil pan which is mounted on the upper crankcase half and which serves as a lower crankcase half provided for collecting and storing oil; at least one coolant jacket connected at an inlet side, for the supply of oil which serves as coolant, via a first supply line to a pump for delivering oil from the oil pan, and at an outlet side, for the discharge of the oil and in order to form an oil circuit, via a first return line to the oil pan, wherein the first return line serves for the gravity-driven discharge of oil whereby at least a part of the oil is, in order to reduce an amount of oil situated in the at least one coolant jacket and thus the cooling power, returned from the at least one coolant jacket of the cylinder block into the oil pan utilizing the force of gravity; a second supply line connecting the pump to a main oil gallery which is provided in the crankcase and which serves for the supply of oil to bearings, wherein the main oil gallery is connected via a second return line, which serves for the gravity-driven discharge of oil, to the oil pan; a discharge line connecting the at least one coolant jacket of the cylinder block to the main oil gallery; and a control unit which has a control drum rotatable about its longitudinal axis between working positions, which control drum in a first working position blocks the first supply line in order to prevent delivery of oil into the at least one coolant jacket of the cylinder block and opens up the second supply line in order to connect the pump to the main oil gallery and supply oil to the bearings.
The internal combustion engine to which the present disclosure relates also has an oil-cooled cylinder block which forms a coherent oil circuit with the oil supply of the internal combustion engine. To form the oil-type cooling arrangement, the cylinder block which serves as an upper crankcase half is equipped with at least one integrated coolant jacket.
The internal combustion engine according to the disclosure has a control drum, by means of the actuation or rotation of which the coolant flow, that is to say the oil flow, can in a suitable way be conducted through the oil circuit or else shut off. In particular, the oil quantity situated in the at least one coolant jacket of the cylinder block can be varied, whereby the amount of heat extracted from the cylinder block by liquid-type cooling can be controlled. The control drum may be of cylindrical form or may have a disk-shaped form, wherein the connections of the lines may then be situated adjacent to the lateral surface of the cylinder or adjacent to the face side of the disk, that is to say may be oriented in the direction of the axis of rotation or transversely with respect to the axis of rotation.
As a result of the discharge of at least a part of the oil by means of a first return line, the cooling power is reduced. Owing to the reduced cooling power and the resulting reduced heat dissipation, the cylinder block heats up more quickly—for example in the warm-up phase of the internal combustion engine—and with the cylinder block the oil situated in the cylinder block also heats up more quickly, said oil comprising not only the oil situated in the at least one coolant jacket but in particular also the residual oil quantities which remain in the consumers and supply lines of the cylinder block even after the shutdown of the internal combustion engine, for example also the oil film which adheres to a cylinder liner, the viscosity of which oil film significantly co-determines the friction between the piston and cylinder liner.
As a result of the discharge of oil from the block, it is the case even while oil is being circulated not only that the cooling power as a result of convection is reduced but basically also that the thermal mass of the block is reduced by the discharged oil quantity, such that a smaller mass needs to be heated up. In particular, the oil which is discharged into the oil pan does not need to be heated.
The internal combustion engine according to the disclosure utilizes the fact that the oil-cooled cylinder block forms a common oil circuit with the oil supply of the internal combustion engine, and the oil of the cooling arrangement can be discharged out of the cylinder block into the oil pan of the oil supply.
The control according to the disclosure of the liquid-type cooling arrangement requires an open circuit, which in the present case is jointly formed by the oil supply of the internal combustion engine, but which for example could not be formed by a water-type cooling arrangement such as is commonly used in internal combustion engines. In the case of a water-cooled cylinder block, it would be necessary for an extraction point for the discharge of the water, a storage vessel, a delivery pump and the like to be provided. It is pointed out that the cylinder head may basically be water-cooled or else may be part of the oil-type cooling arrangement.
The above-described embodiment of the internal combustion engine in interaction with the use of oil as coolant permits, for the first time, the discharge of the cooling liquid.
In principle, the discharge of oil influences or reduces not only the amount of coolant in the at least one coolant jacket but rather also the heat transfer surface between the oil and the block. The possibility of discharging oil of the liquid-type cooling arrangement from the cylinder block permits cooling of the block according to requirements.
It is also the case in the cooling arrangement according to the disclosure that the pump power, and thus also the coolant throughput, that is to say the delivery volume, can be adjusted. In this way, it is possible to influence the throughflow speed, which significantly co-determines the heat transfer by convection. In this way, it is possible for less or more heat to be extracted from the cylinder block.
The discharge of oil according to the disclosure is to be distinguished from a discharge of the oil via the second return line into the oil pan, wherein the oil quantity situated in the at least one coolant jacket does not change or should not change because the recirculated oil quantity is replaced continuously by oil fed via supply lines.
The internal combustion engine according to the disclosure has proven to be particularly advantageous during the warm-up phase, in particular after a cold start. During a restart of the internal combustion engine, the oil quantity in the cylinder block is preferably at a minimum, for example as a result of oil discharge after a standstill period. The cylinder block warms up relatively quickly owing to the combustion processes taking place, whereby already directly after the start, relatively large amounts of heat are introduced into the residual oil situated in the cylinder block. The oil situated in the cylinder block is consequently heated more quickly and more quickly attains the low viscosity required for lower friction losses. As a result, the fuel consumption of the internal combustion engine is noticeably reduced.
During said heating-up phase, that is to say warm-up phase, the rotatable control drum of the internal combustion engine according to the disclosure is preferably situated in a first working position in which the first supply line is blocked, in order to prevent the delivery of oil into the at least one coolant jacket of the cylinder block. In this way, during the heating-up phase, no oil is delivered through the at least one coolant jacket of the cylinder block, and the oil quantity situated in the cylinder block is kept small and is not enlarged. Here, since the main oil gallery cannot be simultaneously supplied with oil via the cylinder block, the second supply line is opened up in order to connect the pump to the main oil gallery, and to be able to supply oil to the bearings, while bypassing the cylinder block.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.